A building automation system is an arrangement for monitoring, open-loop control and/or closed-loop control of process variables in complex technical systems in a building, or in a campus comprising a number of buildings. A building automation system typically operates heating, ventilation and air-conditioning systems, lighting and shading devices and also access control, security and fire surveillance systems. In the building automation system process variables—such as room air conditioning variables or events for example—are detected, evaluated, monitored, influenced or generated, with the energy consumption of the building or campus also advantageously being optimized by the building automation system.
Generally, a building automation system encompasses and operates a plurality of what are known as field devices, such as sensors and actuators. Examples of typical field devices are temperature and humidity sensors, air quality sensors, pressure sensors, flow meters, electricity meters, heat meters, brightness sensors, fire alarms, intrusion alarms, alarm or sprinkler devices, drives for hot water valves, thermostat valves, ventilation flaps or blinds, light switches, smart card readers or devices for detecting biometric data. The building automation system typically comprises a plurality of software modules, processes or programs, and in general a number of computers or processors for their activation and also as a rule a plurality of open-loop and closed-loop control devices as well as further devices, for example devices for linking the building automation system to external communication networks, screens of devices for analysis of video signals.
The elements (HVAC physical objects or field devices) of a building automation system are widely dispersed throughout a facility. For example, an HVAC system includes temperature sensors and ventilation damper controls as well as other elements that are located in virtually every area of a facility. Similarly, a security system may have intrusion detection, motion sensors and alarm actuators dispersed throughout an entire building or campus. Likewise, fire safety systems include smoke alarms and pull stations dispersed throughout the facility. To achieve efficient and effective building automation system operation, there is a need to monitor the operation of, and often communicate with, the various dispersed elements of a building automation system.
Electrical or wireless communication media are used in a building automation system for the exchange of data of individual devices or parts of systems, as a rule a number of communication networks exist, with cables, optical data communication channels, ultrasound connections, electromagnetic near fields or radio networks able to be used, including fiber optic networks or cellular networks for example. Examples of technologies or standards able to be used for the said data exchange are BACnet, LON or LonWorks® from the company ECHELON, the European Installation bus EIB, KONNEX, ZigBee or PROFIBUS defined by German standard DIN 19245.
Building automation systems typically have one or more centralized control stations in which data from each of the elements in the system may be monitored and in which various aspects of system operation may be controlled and/or monitored. The control station typically includes a computer having processing equipment, data storage equipment, and a user interface. To allow for monitoring and control of the dispersed control system elements, building automation systems often employ multi-level communication networks to communicate operational and/or alarm information between operating elements, such as sensors and actuators, and the centralized control station.
One example of a building automation system control station is the APOGEE® INSIGHT® Workstation, available from Siemens Industry, Inc. of Buffalo Grove, Ill., which may be used with the model APOGEE® building automation system, also available from Siemens Industry, Inc. (APOGEE and INSIGHT are U.S federally registered trademarks of Siemens Industry, Inc.) In this system, several control stations, connected via an Ethernet or another type of network, may be distributed throughout one or more building locations, each having the ability to monitor and control system operation. As a consequence, different people in different locations of the facility may monitor and control building operations.
The typical building automation system (including those utilizing the APOGEE® Insight® Workstation) has a plurality of field panels and/or controllers that are in communication with a workstation. In addition, the building automation system also includes one or more field devices connected to the field panels and/or controllers. Each field device is typically operative to measure, monitor, and/or control various building automation system parameters and/or functions. In particular, each field device may include one or more sensors and/or actuators to measure, monitor, and/or control corresponding “points” within the respective building and/or building automation system. As referenced herein, a “point” may be (i) any physical input or output to or from a respective controller, field device, sensor or actuator, or (ii) any virtual point associated with a control application or logic object within a controller or field panel that is measured, monitored or controlled. While the workstation is generally used to make modifications and/or changes to one or more of the various components of the building automation system, a field panel may also be operative to enable certain modifications and/or changes to one or more parameters of the system. This typically includes parameters such as a temperature set point or other set points in a field device controller or directly in a field device. In addition, the workstation may be configured to modify a control program or the like in a field panel for controlling a field device. In addition, a workstation may include a human interface into the system; a field panel may connect to field devices to run automatic programs that read data from input devices and execute commands to output devices.
Ensuring that related HVAC devices operate such that one device does not harm or cause an error with respect to another device is difficult and programming intense. Such programs typically make use of complex ANDs, ORs, and arithmetic functions to provide assurances that HVAC devices will not harm or operate counter to another device. Such device requirements are typically referred to as “interlocks.” For example, a device may only fulfill its physical function if another device supports it in the case of a heating coil in a duct with a fan. Hot air will not be discharged from the heating coil unless the fan moves the air through the coil. Thus, the heating coil device must send a signal to the fan device requesting the fan to run. By way of another example, a device may cause damage if it runs without another in the case of a fan in a 100% outside air supply duct with an outside air damper. If the fan runs without first receiving a damper-open status signal, the duct on the inlet of the fan can collapse due to the unrelieved suction. Another example includes that two devices can cause damage if they operate together. Still other examples include a time delay that should be included with an interlock such as in the case of an electric heating coil that continues to send a hold request for air flow to the fan for five minutes after the heating coil turns off to dissipate residual heat in the coil. Still other examples include when two similar devices share load and run-time (Lead-Lag control) requiring coordinated control of lead-lag between the lead device and the lag device.